Transmission characteristic measuring device transmission characteristic measuring method, and amplifier

ABSTRACT

A transfer characteristics measuring device automatically measures the transfer characteristics of each channel of a multi-channel acoustic reproduction system in a multi-channel acoustic reproduction environment, while allowing normal multi-channel reproduction to proceed. The transfer characteristics measuring device ( 5 ) comprises an object of measurement selecting section ( 51 ) that selects one of the objects of measurement according to the levels of the input signals for five channels being supplied to the objects of measurement and a transfer characteristics computing and determining section ( 52 ) that computes and determines the transfer characteristics of the object of measurement selected by the object of measurement selecting section ( 51 ).

TECHNICAL FIELD

This invention relates to a transfer characteristics measuring deviceand a transfer characteristics measuring method for measuring thetransfer characteristics of an object of measurement, using an inputsignal being input to the object of measurement and an output signaloutput from the object of measurement in a multi-channel acousticreproduction environment. The present invention also relates to atransfer characteristics measuring computer program to be executed by atransfer characteristics measuring device for measuring the transfercharacteristics of an object of measurement. The present inventionfurther relates to an amplifier containing a transfer characteristicsmeasuring device for measuring the transfer characteristics of an objectof measurement.

The present application claims priority from Japanese Patent ApplicationNo. 2002-129307 filed on Apr. 30, 2002, entire contents of which arehereby incorporated by reference into this application.

BACKGROUND ART

Standards have been provided for digital versatile discs (DVDs), ordigital video discs, super audio compact discs (SACDs) and so on asmediums adapted to multi-channel reproduction using two or more than twoindependent channels.

The provisions on the positions of multi-channel speakers in thesestandards are based on the ITU-R (International Telecommunications UnionRadio-communication Sector) recommendation BS-775-1 “Multi-channelStereophonic Sound System with and without Accompanying Picture”.

FIG. 1 of the accompanying drawings schematically illustrates a standardspeaker arrangement for a multi-channel stereophonic sound systemaccording to the recommendation. The illustrated speaker arrangementinvolves 5 channel speakers including a front left channel L, a frontright channel R, a front center channel C, a surround left channel LSand a surround right channel RS as arranged relative to listener U. Aso-called 5.1 channel arrangement obtained by adding a sub-woofer (SW)speaker for low frequency enhancement (LFE) as shown in FIG. 2 is also astandard arrangement.

On the other hand, an audio reproduction device for replaying such amulti-channel medium is provided with independent audio reproductioncircuits and so many audio output terminals, the number of whichcorresponds to the maximum number of channels that the multi-channelmedium has. If an optical disc stores an audio source having 5 channelsor 5.1 channels, the output terminals of the reproduction device forreplaying the optical disc are connected to an external amplifier having5 or 5.1 channel input terminals and the external amplifier is connectedto the speakers corresponding to the 5 channels or 5.1 channels.

Meanwhile, when measuring the acoustic characteristics of each channelin a multi-channel acoustic reproduction environment where a DVD is usedas audio source, a pink noise or white noise that is called test tone isreproduced for each channel so as to be heard by the user and theinter-channel level difference, if any, is manually adjusted by a usertypically by means of a remote control unit.

Some expensive high quality AV amplifiers are provided with a functionalfeature of automatically adjusting the level difference and thedifference in the propagation distance. With such a feature, a gaugingmicrophone is placed at a listening position and the amplifier isequipped in the inside thereof with a test generator. A test tone isreproduced on a channel by channel basis so as to be picked up by themicrophone. Then, the signal representing the picked up test tone isused to compare the picked up test tone with the original test tone tomeasure the inter-channel level difference and the difference in thepropagation distance (time) among the channels for automatic adjustment.

With any of the above described systems to be used in a multi-channelacoustic reproduction environment, a test tone needs to be reproducedfor each channel.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a transfercharacteristics measuring device and a transfer characteristicsmeasuring method that can automatically measure the transfercharacteristics of each channel of a multi-channel acoustic reproductionsystem in a multi-channel acoustic reproduction environment, whileallowing normal multi-channel reproduction to proceed.

Another object of the present invention is to provide a transfercharacteristics measuring computer program that can make a computer tooperate as a transfer characteristics measuring device thatautomatically measures the transfer characteristics of each channel of amulti-channel acoustic reproduction system in a multi-channel acousticreproduction environment, while allowing the system to operate fornormal multi-channel reproduction.

Still another object of the present invention is to provide an amplifierin which the transfer characteristics of each channel is automaticallymeasured in a multi-channel acoustic reproduction environment.

In an aspect of the present invention, the above objects are achieved byproviding a transfer characteristics measuring device for measuring thetransfer characteristics of each of n objects of measurement out of m(n≦m) objects of measurement, using the input signals being input to them objects of measurement and the output signals from the objects ofmeasurement in an acoustic reproduction environment for m channelshaving mutually differentiated respective spatial positions, the devicecomprising: an object of measurement selecting means for selecting anobject of measurement out of the n objects of measurement according tothe levels of the input signals of the m channels being supplied to them objects of measurement; and a transfer characteristics computing anddetermining means for computing the transfer characteristics of theobject of measurement selected by the object of measurement selectingmeans according to the input signal being supplied to the object ofmeasurement and the output signal of the object of measurementcorresponding to the input signal, determining adoption of the transfercharacteristics of the object of measurement and excluding the object ofmeasurement from the m objects of measurement.

Thus, the object of measurement selecting means selects an object ofmeasurement out of the n (n≦m) objects of measurement according to thelevels of the input signals of the m channels being supplied to the mobjects of measurement. The transfer characteristics computing anddetermining means computes the transfer characteristics of the object ofmeasurement selected by the object of measurement selecting meansaccording to the input signal being supplied to the object ofmeasurement and the output signal of the object of measurementcorresponding to the input signal, determines adoption of the transfercharacteristics of the object of measurement and excludes the object ofmeasurement from the m objects of measurement.

So far, it has been made clear that the acoustic characteristics of a1-channel acoustic reproduction device can be measured by means of amethod of measuring acoustic characteristics including the amplitude atthe listening position and the impulse response (propagation time) ofthe acoustic reproduction device, using the sound of a piece of music orthat of a movie film but not using a measurement signal of noise orimpulse, picking up the sound reproduced from the acoustic reproductiondevice by means of a microphone at the listening position and analyzingthe original signal being input to the acoustic reproduction device andthe signal of the sound picked up by the microphone by means of adiscrete cross spectrum method.

To the contrary, according to the present invention, it is possible toautomatically measure and regulate the acoustic characteristics of eachof a plurality of channels without taking out a test tone from thechannel, while allowing normal multi-channel reproduction to proceed ina multi-channel acoustic reproduction environment, by measuring thetransfer characteristics by means of a discrete cross spectrum method.

Thus, according to the invention, it is possible to automaticallymeasure the acoustic characteristics of each of a plurality of channelsfor all the channels, using a reproduction source signal of themulti-channel, in a multi-channel acoustic reproduction environmentwhere the multi-channel reproduction source signal is reproduced by areproduction device for a DVD or the like that is connected to anamplifier such as an AV amplifier, which accommodates the multi-channeland is further connected to speakers.

After the measurement, the channels are automatically regulated byregulating the parameters of the AV amplifier.

In another aspect of the invention, there is provided a transfercharacteristics measuring device for measuring the transfercharacteristics of each of n objects of measurement out of m (n≦m)objects of measurement, using the input signals being input to the mobjects of measurement and the output signals from the objects ofmeasurement in an acoustic reproduction environment for m channelshaving mutually differentiated respective spatial positions, the devicecomprising: an object of measurement selecting means for selecting anobject of measurement out of the m objects of measurement according tothe levels of the input signals of the m channels being supplied to them objects of measurement; and a transfer characteristics computing anddetermining means for computing the transfer characteristics of theobject of measurement selected by the object of measurement selectingmeans according to the input signal being supplied to the object ofmeasurement and the output signal of the object of measurementcorresponding to the input signal for each frequency point and adoptingthe transfer characteristics of the object of measurement in concurrencewith computing and adopting the transfer characteristics of each of theobjects of measurement selected by the object of measurement selectingmeans from the n objects of measurement.

Thus, the object of measurement selecting means selects an object ofmeasurement according to the levels of the input signals of the mchannels being supplied to the m objects of measurement. The transfercharacteristics computing and determining means computes the transfercharacteristics of the object of measurement according to the inputsignal being supplied to the object of measurement and the output signalof the object of measurement corresponding to the input signal for eachfrequency point and adopts the transfer characteristics of the object ofmeasurement in concurrence with computing and adopting the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting means from the n objects of measurementfor each frequency point.

In still another aspect of the invention, there is provided a transfercharacteristics measuring method for measuring the transfercharacteristics of each of n objects of measurement out of m (n≦m)objects of measurement, using the input signals being input to the mobjects of measurement and the output signals from the objects ofmeasurement in an acoustic reproduction environment for m channelshaving mutually differentiated respective spatial positions, the methodcomprising: an object of measurement selecting step of selecting anobject of measurement out of the n objects of measurement according tothe levels of the input signals of the m channels being supplied to them objects of measurement; and a transfer characteristics computing anddetermining step of computing the transfer characteristics of the objectof measurement selected in the object of measurement selecting stepaccording to the input signal being supplied to the object ofmeasurement and the output signal of the object of measurementcorresponding to the input signal, determining adoption of the transfercharacteristics of the object of measurement and excluding the object ofmeasurement from the m objects of measurement.

In still another aspect of the invention, there is provided a transfercharacteristics measuring method for measuring the transfercharacteristics of each of n objects of measurement out of m (n≦m)objects of measurement, using the input signals being input to the mobjects of measurement and the output signals from the objects ofmeasurement in an acoustic reproduction environment for m channelshaving mutually differentiated respective spatial positions, the methodcomprising: an object of measurement selecting step of selecting anobject of measurement according to the levels of the input signals ofthe m channels being supplied to the m objects of measurement; and atransfer characteristics computing and determining step of computing thetransfer characteristics of the object of measurement selected in theobject of measurement selecting step according to the input signal beingsupplied to the object of measurement and the output signal of theobject of measurement corresponding to the input signal for eachfrequency point and adopting the transfer characteristics of the objectof measurement in concurrence with computing and adopting the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting step from the n objects of measurementfor each frequency point.

In still another aspect of the invention, there is provided a transfercharacteristics measuring computer program to be executed by a transfercharacteristics measuring device for measuring the transfercharacteristics of each of n objects of measurement out of m (n≦m)objects of measurement, using the input signals being input to the mobjects of measurement and the output signals from the objects ofmeasurement in an acoustic reproduction environment for m channelshaving mutually differentiated respective spatial positions, thecomputer program comprising: an object of measurement selecting step offor selecting an object of measurement out of the n objects ofmeasurement according to the levels of the input signals of the mchannels being supplied to the m objects of measurement; and a transfercharacteristics computing and determining step of computing the transfercharacteristics of the object of measurement selected in the object ofmeasurement selecting step according to the input signal being suppliedto the object of measurement and the output of the object of measurementcorresponding to the input signal, determining adoption of the transfercharacteristics of the object of measurement and excluding the object ofmeasurement from the m objects of measurement.

In still another aspect of the invention, there is provided a transfercharacteristics measuring computer program to be executed by a transfercharacteristics measuring device for measuring the transfercharacteristics of each of n objects of measurement out of m (n≦m)objects of measurement, using the input signals being input to the mobjects of measurement and the output signals from the objects ofmeasurement m an acoustic reproduction environment for m channels havingmutually differentiated respective spatial positions, the computerprogram comprising: an object of measurement selecting step of selectingan object of measurement according to the levels of the input signals ofthe m channels being supplied to the m objects of measurement; and atransfer characteristics computing and determining step of computing thetransfer characteristics of the object of measurement selected in theobject of measurement selecting step according to the input signal beingsupplied to the object of measurement and the output signal of theobject of measurement corresponding to the input signal for eachfrequency point and adopting the transfer characteristics of the objectof measurement in concurrence with computing and adopting the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting means from the n objects of measurementfor each frequency point.

In still another aspect of the invention, there is provided an amplifiercontaining a transfer characteristics measuring device for measuring thetransfer characteristics of each of n amplifiers out of m (n≦m)amplifiers, using the input signals being input to the m amplifiers andthe output signals from the amplifiers in an acoustic reproductionenvironment for m channels having mutually differentiated respectivespatial positions, the device comprising: an object of measurementselecting means for selecting an amplifiers out of the n objects ofmeasurement according to the levels of the input signals of the mchannels being supplied to the m amplifiers; and a transfercharacteristics computing and determining means for computing thetransfer characteristics of the amplifier selected by the object ofmeasurement selecting means according to the input signal being suppliedto the amplifier and the output signal of the amplifier corresponding tothe input signal, determining adoption of the transfer characteristicsof the amplifier and excluding the amplifier from the m amplifiers.

In a further aspect of the invention, there is provided an amplifiercontaining a transfer characteristics measuring device for measuring thetransfer characteristics of each of n amplifiers out of m (n≦m)amplifiers, using the input signals being input to the m amplifiers andthe output signals from the amplifiers in an acoustic reproductionenvironment for m channels having mutually differentiated respectivespatial positions, the device comprising: an object of measurementselecting means for selecting an amplifier out of the n objects ofmeasurement according to the levels of the input signals of the mchannels being supplied to the m amplifiers; and a transfercharacteristics computing and determining means for computing thetransfer characteristics of the object of measurement selected by theobject of measurement selecting means according to the input signalbeing supplied to the object of measurement and the output signal of theobject of measurement corresponding to the input signal for eachfrequency point and adopting the transfer characteristics of the objectof measurement in concurrence with computing and adopting the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting means from the n objects of measurementfor each frequency point.

Other objects and specific advantages of the present invention willbecome apparent from the detailed description given below by referringto the accompanying drawings that illustrate preferred embodiments ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the positional arrangement ofspeakers of a 5-channel acoustic reproduction system;

FIG. 2 is a schematic illustration of the positional arrangement ofspeakers of a 5.1-channel acoustic reproduction system;

FIG. 3 is schematic illustration of the configuration of a 5-channelacoustic reproduction system;

FIG. 4 is a detailed schematic illustration of the object of measurementselecting section of a transfer characteristics measuring deviceaccording to the invention;

FIG. 5 is a detailed schematic illustration of the transfercharacteristics computing section of the transfer characteristicsmeasuring device according to the invention;

FIG. 6 is a detailed schematic illustration of the transfercharacteristics determining section of the transfer characteristicsmeasuring device according to the invention;

FIG. 7 is a flow chart of the processing operation of the transfercharacteristics measuring device according to the invention;

FIG. 8 is a flow chart of a first specific example of the processingoperation of selecting an object channel of measurement out of thechannels that are objects of measurement;

FIG. 9 is a flow chart of the processing operation of computing thetransfer function and the coherence on the basis of FFT;

FIG. 10 is a graph illustrating the average coherence relative to eachfrequency point as example of characteristics;

FIG. 11 is a flow chart of the processing operation of measuring thedelay time;

FIG. 12 is a flow chart of a second specific example of the processingoperation of selecting an object channel of measurement out of thechannels that are objects of measurement;

FIG. 13 is a flow chart of a third specific example of the processingoperation of selecting an object channel of measurement out of thechannels that are objects of measurement;

FIG. 14 is a schematic illustration of the configuration of a5.1-channel acoustic reproduction system; and

FIG. 15 is a schematic illustration of the configuration of a personalcomputer.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described further by referring to theaccompanying drawings that illustrate preferred embodiments of theinvention. Firstly, an embodiment of transfer characteristics measuringdevice according to the invention that is adapted to measure thetransfer characteristics of each of the objects of measurement in a5-channel acoustic reproduction system in an acoustic reproductionenvironment for a multi-channel arrangement having mutuallydifferentiated respective spatial positions. The transfercharacteristics measuring device is adapted to measure the transfercharacteristics of each of the objects of measurement such asamplifiers, using the music recorded in five channels or the sound of amovie film. The transfer characteristics measuring device will bedescribed in grater detail hereinafter.

Firstly, the configuration of a 5-channel acoustic reproduction systemwill be described. The 5-channel acoustic reproduction system is asystem for outputting the 5-channel audio signals reproduced from anoptical disc where a 5-channel audio source is recorded and whichtypically conforms to the DVD standards from respective speakers thataccommodate the 5-channel audio signals. The five channels include afront left channel L, a front center channel C, a front right channel R,a surround left channel LS and a surround right channel RS as arrangedrelative to listener.

As shown in FIG. 3, the 5-channel acoustic reproduction system 1comprises an amplifier section 2 for amplifying the 5-channel analogaudio signals supplied from an optical disc reproduction section (notshown), a speaker section 3 for outputting the analog audio signalsamplified by the amplifier section 2, a microphone 4 for picking up thesounds output from the speakers of the speaker section 3, a transfercharacteristics measuring device 5 for measuring the transfercharacteristics of each of the amplifiers of the amplifier section 2.

The optical disc reproduction section (not shown) comprises an opticalpickup for reading a recorded signal from an optical disc conforming tothe DVD (digital versatile disc) standards, an RF amplifier foramplifying the signal read by the optical pickup, a servo/signalprocessing section for generating a servo signal from the signalamplified by the RF amplifier and processing the amplified signal forthe purpose of detection of the recording pattern and error correction,a mechanism section for driving the optical pickup and the optical discto revolve according to the servo signal generated by the servo/signalprocessing section and a decoder section for converting the signalprocessed by the servo/signal processing section into independentdigital audio signals for the 5 channels. The audio reproduction sectionincludes a D/A converter section for converting the independent digitalaudio signals for five channels obtained by the decoder section intorespective analog audio signals for five channels.

The amplifier section 2 receives the analog audio signals for fivechannels from the D/A converter section respectively by way of the inputterminals 21 _(L), 21 _(C), 21 _(R), 21 _(LS), 21 _(RS) and amplifiesthem by the respective amplifiers 22 _(L), 22 _(C), 22 _(R), 22 _(LS),22 _(RS) in the amplifier section 2.

The speaker section 3 includes a speaker 31 _(L) for the left channel, aspeaker 31 _(C) for the center channel, a speaker 31 _(R) for the rightchannel, a speaker 31 _(LS) for the left surround channel and a speaker31 _(RS) for the right surround channel and outputs the analog audiosignals supplied from the amplifier section 2 for the channels.

The microphone 4 is a microphone for measurement arranged at thelistening position of the listener. It picks up the music or the soundof a movie film recorded in five channels, converts it into an electricsignal and supplies it to the transfer characteristics measuring device5.

The transfer characteristics measuring device 5 comprises an object ofmeasurement selecting section 51 for selecting one of the objects ofmeasurement according to the levels of the input signals for fivechannels being supplied to the objects of measurement and a transfercharacteristics computing and determining section 52 for computing anddetermining the transfer characteristics of the object of measurementselected by the object of measurement selecting section 51.

The object of measurement selecting section 51 selects one of theobjects of measurement according to the levels of the input analog audiosignals of the front left channel L, the front center channel C, thefront right channel R, the surround left channel LS and the surroundright channel RS before the signals are input to the respectiveamplifiers 22 _(L), 22 _(C), 22 _(R), 22 _(LS), 22 _(RS) of theamplifier section 2.

As shown in FIG. 4, the object of measurement selecting section 51includes an intake section 511 for taking in the input signals for fivechannels supplied respectively to the objects of measurements for fivechannels, a level detecting section 512 for detecting the levels of theinput signals for five channels that are taken in by the intake section511 and a selecting section 513 for selecting one of the objects ofmeasurement according to the levels detected by the level detectingsection 512.

The intake section 511 has a buffer memory for the L-CH, a buffer memoryfor the R-CH, a buffer memory for the C-CH channel, a buffer memory forthe LS-CH channel and a buffer memory for the RS-CH, all of which have acapacity sufficient for taking in as many audio signals for the Lchannel, R channel, C channel, LS channel, RS channel converted by anA/D converter (not shown) into digital audio signals as the number ofpoints P, which will be described in greater detail hereinafter.

The level detecting section 512 detects the levels of the data that theintake section 511 takes into the buffer memories and makes theselecting section 513 select the channel of the highest level. The leveldetecting section 512 detects the levels of the data on a peak to peakbasis. It may transform the levels onto the frequency axis by He andmeasure them, using a frequency band of 500 Hz to 2 kHz, for example. Itmay measure the levels by normalization (RMS).

The level detecting section 512 checks the level of the audio signaltaken in by the intake section 511 in this way for each channel and theselecting section 513 selects the channel whose audio signal shows avolume level higher than a predetermined level and the greatest levelvalue of all the signals for the five channels as object of measurementchannel.

The transfer characteristics computing and determining section 52includes an orthogonal transformation section for performing anorthogonal transformation on the input signals supplied to the object ofmeasurement, which is selected by the object of measurement selectingsection 51, and the output signals of the object of measurement thatcorrespond to the input signals, a power spectrum computing section forcomputing the power spectrums of the input signals and those of theoutput signals, using the spectrums of the input signals and those ofthe output signals obtained by the orthogonal transformation section, across spectrum computing section for multiplying the frequency componentof the spectrum of each input signal by that of the spectrum of thecorresponding output signal obtained by the orthogonal transformationsection to computationally determine the cross spectrums, a spectrumaverage computing section for computing the average of the powerspectrums of the input signals and the average of the power spectrums ofthe output signals computed by the power spectrum computing section andthe average of the cross spectrums computed by the cross spectrumcomputing section, a transfer characteristics computing section forcomputing the transfer characteristics of the object of measurement fromthe averages of the power spectrums and the average of the crossspectrums computed by the spectrum average computing section, acoherence computing section for computing the value of the coherencefrom the average value of the power spectrums of the input signals, theaverage value of the power spectrums of the output signals and theaverage value of the cross spectrums computed by the spectrum averagecomputing section and a transfer characteristics determining section fordetermining adoption of the transfer characteristics of the object ofmeasurement computed by the transfer characteristics computing sectionon the basis of the coherence value computed by the coherence computingsection and excluding the object of measurement from the plurality ofobjects of measurement, the number of which is equal to m.

FIG. 5 illustrates a principal part of the transfer characteristicscomputing and determining section 52 in detail. Referring to FIG. 5, theinput IN₁ obtained by digital conversion of the input signal to theobject of measurement selected by the object of measurement selectingsection 51 is supplied to input terminal 61. The input IN₂ obtained bydigital conversion of the output signal of the object of measurementthat corresponds to the input signal IN₁ is supplied to input terminal71.

The number of samples of audio signal necessary for measuring thetransfer characteristics is computed by using the number of points offast Fourier transformation (FFT), which is a specific example oforthogonal transformation as will be described hereinafter and thenumbers of times of averaging the power spectrums and the crossspectrums, which will also be described hereinafter. If, for example,the number of samples necessary for measuring the transfercharacteristics is S, the number of points of fast Fouriertransformation is P and the number of times of averaging is N, thenumber of samples S necessary for measuring the transfer characteristicsis expressed by formula (1) below.S=P×N  (1)

More specifically, if the number of points P of fast Fouriertransformation is 65,536 and the number of times of averaging N is 4,the number of samples is 65,536×4.

If the number of samples S needs to be computed accurately by using arelatively large number of points as in the case where the transfercharacteristic that is selected as object of measurement is thefrequency characteristic (transfer function), the number of points willbe 65,536. However, when a detailed response is not required as in thecase where the delay time is determined approximately from the impulseresponse, the number of points may be 1024 or 2048. The use of a largenumber of points is not required because it is only necessary to knowthe peak position of the impulse response. The number of times ofaveraging is not limited to 4 or 10. It may be 1, 2, 3, 5, 6, 7 or 9depending on the transfer characteristic that is selected as object ofmeasurement. Alternatively, the number of times of averaging may be 20,25 or 30.

In this specific example, the signal data are taken out from the headthereof as signal of the input IN₂ and signal data of the correctingpart are taken out from the head thereof by delaying it as signal of theinput IN₁ to consider an occasion where the signal of the input IN₂ isdelayed relative to the signal of the input IN₁ beyond the limit of thenumber of points of fast Fourier transformation.

The signal of the input IN₁ is output from the input terminal 61 tomultiplier 63 and the signal of the input IN₂ that corresponds to thesignal of the input IN₁ is output from the input terminal 71 tomultiplier 73.

When the sound waveforms of a predetermined sample number are taken out,it is necessary to be careful so as not to give rise to a sharp changeat the opposite ends of the taken out part and the original waveform hasto be multiplied by a time window in the spectrum range in order toconvolute the Fourier transformation of the window function for thespectrum of the signal, or obtain a weighted moving average. Thus,window functions that respectively correspond to the bands of thesignals transmitted to the above multipliers 63, 73 are generated bywindow function generators 62,72 and supplied to the multipliers 63, 73.As a result, the multipliers 63, 73 respectively multiply the signals ofthe bands by the window functions and the signals obtained by themultiplications are respectively sent to FFT analyzers 64, 74.

The FFT analyzers 64, 74 determine the frequency spectrum of the signalof the input IN₁ and the frequency spectrum of the signal of the inputIN₂ by performing an operation of fast Fourier transformation on thesignal data transmitted to them.

If the complex data of the spectrum of the input IN₁ is X(k), thecomplex data X(k) is sent to multiplier 66 and also to complex conjugatetransformer 65. The complex conjugate transformer 65 transforms thecomplex data X(k) transmitted to it into complex conjugate data X*(k)and transmits the latter to the multiplier 66. The multiplier 66multiplies the complex data X(k) from the FFT analyzer 64 by the complexconjugate data X*(k) to obtain the power spectrum X*(k) X(k) of theinput IN₁. The power spectrum X*(k) X(k) is stored in register 81 a.

Similarly, if the complex data of the spectrum of the input IN₂ is Y(k),the complex data Y(k) is sent to multiplier 76 and also to complexconjugate transformer 75. The complex conjugate transformer 75transforms the complex data Y(k) transmitted to it into complexconjugate data Y*(k) and transmits the complex conjugate data Y*(k) tothe multiplier 76. The multiplier 76 multiplies the complex data Y(k)from the FFT analyzer 74 by the complex conjugate data Y*(k) to obtainthe power spectrum Y*(k) Y(k) of the input IN₂. The power spectrum Y*(k)Y(k) is stored in register 81 c.

The complex conjugate data X*(k) of the spectrum of the input IN₁ outputfrom the complex conjugate transformer 65 is multiplied by the complexdata Y(k) of the spectrum of the input IN₂ output from the FFT analyzer74 to obtain the cross spectrum X*(k) Y(k) by the multiplier 67, whichcross spectrum X*(k) Y(k) is stored in register 81 b.

In fact, there are provided as many registers 81 a, 81 b, 81 c as thenumber equal to N that corresponds to the number of time of averaging N.In other words, N power spectrums X*(k) X(k) for N inputs IN₁, N powerspectrums Y*(k) Y(k) for N inputs IN₂ and N cross spectrums X*(k) Y(k)are stored in the respective registers.

Subsequently, the N power spectrums X*(k) X(k) for the N inputs IN₁, theN cross spectrums X*(k) Y(k) and the N power spectrums Y*(k) Y(k) forthe N inputs IN₂ that are stored in the respective registers 81 a, 81 b,81 c are transmitted respectively to averaging circuits 82 a, 82 b, 82 cso that the average value P₁(k) of the power spectrums of the inputsIN₁, the average value C(k) of the cross spectrums and the average valueP₂(k) of the power spectrums of the inputs IN₂ are computed.

Note that the average value P₁(k) of the power spectrums of the inputsIN₁ is expressed by formula (2) below and the average value P₂(k) of thepower spectrums of the inputs IN₂ is expressed by formula (3) below,while the average value C(k) of the cross spectrums is expressed byformula (4) below.P ₁(k)= X*(k)X(k) X*(k)X(k)  (2)P ₂(k)= Y*(k)Y(k) Y*(k)Y(k)  (3)C(k)= X*(k)Y(k) X*(k)Y(k)  (4)

The average value P₁(k) of the power spectrums of the inputs IN₁ and theaverage value C(k) of the cross spectrums are transmitted to transferfunction computing unit 85, which transfer function computing unit 85computes the transfer function H(k) of the object of measurement. Morespecifically, the amplitude and the phase are computed as transferfunction. The value of the transfer function is output from outputterminal 87.

The transfer function H(k) including the amplitude and the phase isexpressed by formula (5) below, while the transfer function H(k)including only the amplitude is expressed by formula (6) below.

$\begin{matrix}{{H(k)} = \frac{C(k)}{P_{1}(k)}} & (5) \\{{H(k)} = \frac{P_{2}(k)}{P_{1}(k)}} & (6)\end{matrix}$

The average value P₁(k) of the power spectrums of the input IN₁, theaverage value P₂(k) of the power spectrums of the inputs IN₂ and theaverage value C(k) of the cross spectrums are sent to coherencecomputing unit 84.

The average value C(k) of the cross spectrums determined by theaveraging circuit 82 b is sent to the complex conjugate transformer 83to obtain the complex conjugate data C*(k) of the average value C(k) ofthe cross spectrums, which complex conjugate data C*(k) of the averagevalue C(k) of the cross spectrums is also sent to the coherencecomputing unit 84.

The coherence computing unit 84 determines the coherence, or theinterfering property of light waves that interfere with each other,using the average value P₁(k) of the power spectrums of the input IN₁,the average value P₂(k) of the power spectrums of the inputs IN₂, theaverage value C(k) of the cross spectrums and the complex conjugate dataC*(k) of the average value C(k) of the cross spectrums. If the coherenceis r, it is expressed by formula (7) below.

$\begin{matrix}{r = \frac{C*(k){C(k)}}{{P_{1}(k)}{P_{2}(k)}}} & (7)\end{matrix}$

The coherence r that is computed by the coherence computing unit 84 issupplied to transfer function determining section 88 as shown in FIG. 6by way of output terminal 85. The transfer function H(k) computed by thetransfer function computing unit 84 is also supplied to the transferfunction determining section 88.

The transfer function determining section 88 determines adoption of thevalue of the transfer function H(k) of an object of measurementaccording to the coherence value r and excludes the object ofmeasurement from the objects of measurement of the five channels. Forexample, the coherence value r (of the transfer function) is adoptedwhen it is not smaller than 0.8 and the channel is excluded from theobjects of measurement by the transfer function determining section 88.

When sounds are reproduced simultaneously from a multi-channelarrangement that may involve the use of five channels, the coherencevalue r may be degraded and low if similar signal components exist witha similar sound volume level both in the channel that is the object ofmeasurement and in some other channel so that the result of themeasurement is disregarded and invalidated. On the other hand, thecoherence value r may be significant and high if the sound levels of thechannels other than the channel that is the object of measurement arelow or if similar signal components do not exist so that the result ofthe measurement is adopted if the coherence value r is not lower than apredetermined value.

Now, a specific processing operation of the transfer characteristicsmeasuring device 5 in the 5-channel acoustic reproduction system will bedescribed by referring to FIG. 7.

Referring to FIG. 7, in Step S1, the object of measurement selectingsection 51 checks if there are five objects of measurement for fivechannels that can be taken in by the intake section 511 or not. Theprocessing operation proceeds to Step S2 if there are five objects ofmeasurement for five channels.

In Step S2, the object of measurement selecting section 51 selects achannel as object of measurement out of the five channels that canequally be objects of measurement. In this letter of specification, thechannel that is selected as object of measurement is referred to asobject channel of measurement. There is a single object channel ofmeasurement and one or more than one channels that are objects ofmeasurement including the object channel of measurement. Immediatelyafter the start of the flow of the processing operation, there are fivechannels that are objects of measurement. When the result of measurementof an object channel of measurement is adopted, the number of objects ofmeasurement is reduced to four to exclude the object channel ofmeasurement.

FIG. 8 is shows a processing operation of selecting an object channel ofmeasurement in Step S2. Referring to FIG. 8, the level detecting section512 of the object of measurement selecting section 51 detects the inputlevels of the five channels that are objects of measurement and taken inby the intake section 511 to the respective buffer memories and supplieschannel information including information on the channel showing thehighest input level to the selecting section 513. The selecting section513 selects the channel showing the highest input level as objectchannel of measurement according to the channel information from thelevel detecting section 512 (Step S2-1). Then, in Step S2-2, theselecting section 513 checks if the input level of the selected objectchannel of measurement selected in Step S2-1 is not lower than apredetermined level or not. If the input level is not lower than thepredetermined level, the selection of the object channel of measurementis finalized and the processing operation proceeds to Step S3 in FIG. 7.Other specific examples of the processing operation of selecting anobject channel of measurement in Step S2 will be described hereinafter.

Returning to FIG. 7, Steps S3 through S8 are dedicated to measuring theinput level of each of the channels. In Step S3, the transfercharacteristics computing and determining section 52 takes in datanecessary for FFT of input IN₁ and input IN₂. More specifically, datafor the number of points=65,536 necessary for fast Fouriertransformation is taken in. At this time, the microphone input signal istaken in from the head of the data of the input signal, while signaldata of the correcting part of the original signal are taken in from thehead thereof after delaying it by means of a delay circuit to consideran occasion where the microphone input signal is delayed relative to theoriginal reproduction source signal beyond the limit of the number ofpoints. Note that the delay time of the delay circuit is initially equalto 0.

Thereafter, in Step S4, the transfer function and the coherence arecomputed according to the FFT analysis. FIG. 9 illustrates thesubroutine for the operation of Step S4.

In Step S4-1, the original waveform of input IN₁ is multiplied by thetime window and subsequently an FFT operation is conducted, and in StepS4-2, the original waveform of input IN₂ is multiplied by the timewindow and subsequently an FFT operation is conducted to obtain thefrequency spectrums of inputs IN₁, IN₂.

In Step S4-3, power spectrum of input IN₁ for each frequency point iscomputed. In Step S44, power spectrum of input IN₂ for each frequencypoint is computed. Subsequently, in Step S4-5, cross spectrum iscomputed using the power spectrums of inputs IN₁, IN₂.

Thereafter, in Step S4-6, it is determined if the processing operationin Steps S4-1 through S4-5 has been repeated for N (=4) times necessaryfor averaging for each frequency point or not. If not, the operationreturns to Step S4-1 to repeat the processing operation in Steps S4-1through S4-5. If, on the other hand, the processing operation has beenrepeated for N (=4) times, it proceeds to Step S4-7, where the averagevalue of the power spectrums of input IN₁, that of the power spectrum ofinput IN₂ and that of the cross spectrums are determined for eachfrequency point.

Then, in Step S4-8, the coherence, or the interfering property of lightwaves that interfere with each other, using the average value of thepower spectrums of the input IN₁, that of the power spectrums of theinput IN₂ and that of the cross spectrums. Then, in Step S49, thetransfer function is computed. Thus, the subroutine of Step S4 iscompleted.

Then, in Step S5 in FIG. 7, the transfer function determining section 88performs a reliability judging operation of determining if there is afrequency point where the coherence is not greater than 0.8 or not. Inother words, it is checked if all the coherences obtained for all thefrequency points as a result of measurement are not smaller than 0.8 ornot. If it is judged in Step S5 that there is no frequency point (NO)where the coherence is not greater than 0.8 and hence the coherences ofall the frequency points are not smaller than 0.8, the processingoperation proceeds to Step S8, where the result of measurement isadopted and the selected channel is excluded from the channels that areobjects of measurement. If, on the other hand, it is found that there isa frequency point where the coherence is not greater than 0.8 in thereliability judging operation of Step S5, the processing operationproceeds to Step S6. It may be needless to say that the transferfunctions of the frequency points for which the coherences are found tobe not smaller than 0.8 are stored in the respective internal orexternal temporary buffer memories by the transfer function determiningsection 88.

In Step S6, the transfer function determining section 88 checks if thenumber of times of repetition of the processing operation in Steps S2through S5 has reached Z or not. The number of times of repetition ischecked to raise the efficiency of measurement by determining thetransfer function by means of interpolation or some other technique aswill be described hereinafter without waiting indefinitely when thecoherence is smaller than 0.8 for a certain frequency point. The valueof Z will be selected so as to be equal to 5, 10, 15 or 20, forinstance. The processing operation from Step S2 will be repeated if Z=10is selected and the number of times of repetition is 9 in Step S6. Theprocessing operation proceeds to Step S7 when the number of times ofrepetition gets to 10.

If, in Step S7, the number of times of repetition has reached Z butthere is at least a frequency point for which the coherence is smallerthan 0.8, the transfer function determining section 88 determines thetransfer function of the frequency point by means of interpolation, forexample, using data preceding data and succeeding data. When theprocessing operation returns to Step S2 because the number of times ofrepetition has not reached Z in Step S7, the computed transfer functionsare averaged for the frequency points whose coherences are not smallerthan 0.8.

The transfer functions for all the frequency points including thetransfer function computed in Step S7 are adopted as results ofmeasurement in Step S8 and excluded from the channels that are objectsof measurement. After the processing operation in Step S8, the operationreturns to Step S1 to start the operation of computing the transferfunction for the next object channel of measurement.

While the processing operation from Step S2 is repeated when the numberof times of repetition has not reached Z, e.g. 10, in Step S6, someother channel may be selected as object channel of measurement in theprocessing sequence of FIGS. 7 and 8.

For example, if the L channel is selected as object channel ofmeasurement in Step S2 and the processing operation proceeds to StepsS3, to S4 and then to S5, where NO is obtained as a result of judgmentto tell that there is at least a frequency point whose coherence is notgreater than 0.8 for 10 kHz and above, the processing operation returnsto Step S2 because the result of judgment is NO in Step S6. Then, the Cchannel may be selected as object channel of measurement in Step S2.

It may be needless to say that for the transfer function of anyfrequency point whose coherence has got to 0.8 in Step S5, the frequencypoint is stored in the temporary buffer memory as address for the Lchannel. In other words, the transfer function of a frequency pointwhose coherence for L channel is not smaller than 0.8 to make thetransfer function reliable is stored in the temporary buffer memory forthe L channel.

In the next measuring session for the C channel, the transfer functionis stored in the temporary buffer memory for the C channel in Step S5for determining the reliability.

Of course, some other channel such as the R channel, the L channel, orthe LS channel may be selected in the course of measuring the transferfunction at each and every frequency point of the C channel.

When the processing operation gets to Step S8, the transfer functions ofthe L channel or the C channel, for example, are stored in therespective temporary buffer memories that correspond to all thefrequency points.

Now, the reliability judging operation of Step S5 will be describedbelow by way of a specific example.

The coherence computed (in Steps S4 through 7) by computing the averageof N times for each spectrum is the average of coherences for eachfrequency point. FIG. 10 is a graph illustrating the average coherencefor each frequency point as example of characteristics. In other words,FIG. 10 shows the average of the coherences obtained by using a numberof times of N to be used for averaging.

As shown in FIG. 10, the coherence is smaller than 0.8 for frequenciessmaller than 100 Hz. The coherence is not smaller than 0.8 from 100 Hzto 10 kHz but it becomes smaller than 0.8 again beyond 10 kHz.

Thus, the transfer function determining section 88 judges that there isat least a frequency point where the coherence is not greater than apredetermined value in the reliability judgment of Step S5 and proceedsto Step S6.

Then, the processing operation in Steps S2 through S5 is repeated inStep S6 until the number of repetition Z gets to 10. If there is atleast a frequency point where the coherence is smaller than 0.8 in afrequency range below 100 Hz or above 10 kHz, the transfer functions forthose frequency ranges are determined by means of interpolation or someother technique.

The transfer functions determined in Step S4 in FIG. 9, or in Step S49in FIG. 11 to be more accurate, are also used for computing othertransfer characteristics at the listening position of the 5-channelacoustic reproduction system. FIG. 11 is a flow chart of the sequence ofthe processing operation of measuring the delay time. The sequence ofoperation of FIG. 11 comes after the processing operation in Step S4-9in FIG. 9, which shows the subroutine of-Step S4 in FIG. 7.

Firstly in Step 511, it is judged if the end flag is ON or not. The endflag is made ON in a processing operation that will be describedhereinafter.

If it is judged that the end flag is not ON, it means that themeasurement of the delay time is not completed and hence the processingoperation proceeds to Step S15.

In Step S15, the average of the coherences computed for each frequencypoint is determined and, if the average value is smaller than apredetermined value, the processing operation returns to Step S3 shownin FIG. 7 to take in inputs IN₁, IN₂ and the operation down to thecomputation of coherence is repeated.

If the average value of the coherences is not smaller than thepredetermined value for each frequency point, the transfer functioncomputed in Step S49 is subjected to inverse fast Fourier transformation(IFFT) in Step S16 to obtain the impulse response h(t) of the object ofmeasurement. Additionally, the peak value of the data from the beginningof the impulse response h(t) to ½ of the number of points of FFT isdetected.

Subsequently, the processing operation proceeds to Step S17 for theoperation of computing the time-energy characteristic. Morespecifically, the data of the impulse response h(t) is converted into adecibel (dB) value. At this time, the decibel value D is obtained byformula (8) below.D=20 log |h(t)|  (8)

Then, in Step S18, the time tPeak where the peak value is detected isdetected. The value that is greatest among all the values obtained byconverting into decibel values, or the value that is not smaller than apredetermined level, −100 dB for instance, and greater than the averageof all the other values by a predetermined value, 40 dB for instance, isregarded as peak value. If the peak value is expressed by DPeak, it isexpressed by formula (9) below.DPeak=20 log |h(tPeak)|  (9)

Thereafter, in Step S19, it is determined if the time where a peak valueexists is detected or not. If it is determined that the time where apeak value exists is detected as a result of the processing operation inStep S19, the processing operation proceeds to Step S20, where thedetected time for the peak value is selected as delay time for theobject of measurement. Then, the end flag is made ON.

If, on the other hand, the obtained data does not satisfy therequirements of being a peak, the processing operation proceeds to StepS19, where is it judged that the time where a peak value exists is notdetected.

Therefore, the processing operation proceeds to Step S21, where it isjudged if the absolute value of the detected peak value is the maximumvalue of the peak values that have been obtained or not. If it isdetermined that the absolute value of the detected peak value is themaximum value of the peak values, the processing operation proceeds toStep S22 to store the peak value and the time of the peak value, theprocessing operation then proceeds to Step S23. If, on the other hand,it is determined in Step S21 that the absolute value of the detectedpeak value is not the maximum value of the peak values, the processingoperation proceeds to Step S23.

In Step S23, the current delay time d of the delay circuit and the timeof the stored maximum value are compared. If it is determined that thedelay time d is greater than the maximum value as a result of thecomparison, the processing operation proceeds to Step S25 to add ¼ ofthe number of points obtained as a result of FFT is added to the currentdelay time d and the processing operation returns to Step S3, where thevalue obtained by adding ¼ of the number of points that is obtained as aresult of FFT to the current delay time d is selected as delay time d ofthe delay circuit and inputs IN₁, IN₂ are taken in for the processingoperation down to the computation of the transfer function and thecoherence in Step S4.

In this way, the delay time d of the delay circuit is increased by ¼ ofthe number of points that is obtained as a result of FFT until a peakvalue is detected and inputs IN₁, IN₂ are taken in for computing theimpulse response.

If, on the other hand, that the maximum value is greater than the delaytime as a result of comparison in Step S23, the processing operationproceeds to Step S24, where the peak value stored in Step S22 isselected as delay time and the end flag is made ON. Then, the processingoperation returns to Step S3, where the delay time from the delaycircuit of input IN₁ is selected as delay time d and inputs IN₁, IN₂ aretaken in for the processing operation down to the computation of thetransfer function and the coherence in Step S4.

If no peak value is detected to the limit of measurement, the end flagis made ON and the largest peak value among the peak values that havebeen detected is selected as delay time d of input IN₁. Then, inputsIN₁, IN₂ are taken in once again for the processing operation down forcomputing the impulse response.

The measurement of the delay time is made to progress in this way and,once it is determined in Step S11 that the end flag is ON, theprocessing operation proceeds to Step S12, where it is determined if theaverage value of the coherences for each frequency point is not smallerthan the predetermined value or not.

If, as a result, it is confirmed that the average value of thecoherences is not smaller than the predetermined value, the processingoperation proceeds to Step S13, where the delay time d of input IN₁ thatis selected for the delay circuit is determined as the result of themeasurement and displayed on a display device to complete the operationof measuring the delay time. If, on the other hand, it is confirmed thatthe average value of the coherences is smaller than the predeterminedvalue, a warning message is displayed on the display device in Step S14to complete the operation of measuring the delay time.

As described above, a transfer characteristics measuring deviceaccording to the invention picks up the audio signal for 5 channels froma 5-channel audio source reproduced by a 5-channel acoustic reproductionsystem at the listening position by means of a microphone 4 andautomatically measures the transfer characteristics of each channel,while allowing normal multi-channel reproduction to proceed.

Of the transfer characteristics measured by a transfer characteristicsmeasuring device according to the invention, the amplitude and the phasethat relate to the transfer function (frequency characteristics), thedelay time and the propagation time are displayed on the displaysection. Additionally, the transfer characteristics measuring device canbe used to update the parameters of each of the amplifiers of theamplifier section that are objects of measurement and regulate eachchannel according to the transfer characteristics.

The processing operation of selecting an object channel of measurementout of a plurality of object channels of measurement of a transfercharacteristics measuring device according to the invention illustratedin FIG. 7 as Step S2 may be replaced by a processing operationillustrated in FIG. 12.

The level detecting section 512 of the object of measurement selectingsection 51 detects the input levels of the five channels that areobjects of measurement and taken in by the intake section 511 to therespective buffer memories and supplies channel information includinginformation on the channel showing the highest input level to theselecting section 513. The selecting section 513 selects the channelshowing the highest input level as object channel of measurementaccording to the channel information from the level detecting section512 (Step S2-1). Then, in Step S2-12, the selecting section 513 checksif the level difference LD between the input level of the object channelof measurement selected in Step S2-11 and any of the input levels of theremaining object channels of measurement is not smaller than apredetermined value T or not. If the difference is not smaller than thepredetermined value T, the selecting section 513 confirms the selectionof the object channel of measurement and the processing operationproceeds to Step S3 in FIG. 7. The predetermined value T may be 10 dB,20 dB or 30 dB.

The processing operation illustrated in FIG. 7 as Step S2 describedabove may be replaced by a processing operation illustrated in FIG. 13.According to the flow chart of FIG. 13, an object channel of measurementis selected when the level of the candidate channel selected by the userbecomes highest in the object channels of measurement. Thus, theremaining part of the processing operation in FIG. 7 also differs fromthe above-described one.

If it is determined in Step S1 that there are channels to be taken in asobjects of measurement and an object channel of measurement is selectedout of the objects of measurement by the user in Step S2-21, the leveldetecting section checks in Step S2-22 if the level of the objectchannel of measurement is highest among the levels of the objectchannels of measurement. If it is determined that the level of theobject channel of measurement is highest among the levels of the objectchannels of measurement, the processing operation proceeds to Step S3and on as illustrated in FIG. 7.

If it is determined in Step S6 that the number of times of repetition issmaller than Z, the operation of measuring the transfer function of theobject channel of measurement selected by the user firstly in Step S2 isrepeated.

For example, if the L channel is selected as object channel ofmeasurement in Step S2, the L channel remains as object channel ofmeasurement while the processing operation in Steps S2 through S6 isrepeated for 2, 3, 4, . . . , 9 times.

Now, another embodiment of the present invention will be described. Thisembodiment of the invention is a transfer characteristics measuringdevice for measuring the transfer characteristics of an object ofmeasurement selected from a 5.1-channel acoustic reproduction systemcomprising five channels including an L channel, a C channel, an Rchannel, an LS channel, which are described above, and an RS channel anda sub-woofer (SW) channel for low frequency enhancement (LFE). Thus, theembodiment measures the transfer characteristics of each of the objectsof measurement, which may be the speakers, using the sound of a piece ofmusic or that of a movie film recorded on 5.1 channels.

A 5.1-channel acoustic reproduction system is a system adapted to outputthe 5.1-channel audio signals reproduced from an optical disc where a5.1-channel audio source is recorded and which typically conforms to theDVD standards from respective speakers that accommodate the 5.1-channelaudio signals.

Thus, as shown in FIG. 14, the 5.1-channel acoustic reproduction systemcomprises an amplifier section 120 for amplifying the 5.1-channel analogaudio signals supplied from an optical disc reproduction section (notshown), a speaker section 130 for outputting the analog audio signalsamplified by the amplifier section 120, a microphone 140 for picking upthe sounds output from the speakers of the speaker section 130, atransfer characteristics measuring device 150.

The amplifier section 120 receives the analog audio signals for 5.1channels from the D/A converter section respectively by way of the inputterminals 121SW, 121L, 121C, 121R, 121LS, 121RS and amplifies them bythe respective amplifiers 122SW, 122L, 122C, 122R, 122LS, 122RS in theamplifier section 120.

The speaker section 130 includes a speaker 131SW for the sub-wooferchannel, a speaker 131L for the left channel, a speaker 131C for thecenter channel, a speaker 131R for the right channel, a speaker 131LSfor the left surround channel and a speaker 131RS for the right surroundchannel and outputs the analog audio signals supplied from the amplifiersection 120 for the channels.

The microphone 140 is a microphone for measurement arranged at thelistening position of the listener. It picks up the music or the soundof a movie film recorded in 5.1 channels, converts it into an electricsignal and supplies it to the transfer characteristics measuring device150.

The transfer characteristics measuring device 150 includes an object ofmeasurement selecting section 151 for selecting one of the objects ofmeasurement according to the levels of the input signals for 5.1channels being supplied to the objects of measurement and a transfercharacteristics computing and determining section 152 for computing anddetermining the transfer characteristics of the object of measurementselected by the object of measurement selecting section 151.

Since the sub-woofer is normally in charge of a very low band lower than120 Hz. Therefore, the band that is lower than 120 Hz, which thesub-woofer can reproduce, can be excluded from the operation ofcomputing the transfer characteristics of the remaining five channels.

As the object of measurement selecting section 151 detects that asub-woofer is found in the system, the transfer characteristicscomputing and determining section 152 of the transfer characteristicsmeasuring device 150 can exclude the very low frequency band from theoperation of computing the transfer characteristics of the remainingfive channels. As a result, the above described processing operation inSteps S7 and S8 in FIG. 7 can be omitted.

Otherwise, the sequence of the processing operation illustrated in FIGS.4 through 13 is applicable to the transfer characteristics measuringdevice 150.

Thus, the transfer characteristics measuring device according to theinvention picks up the audio signal for 5.1 channels from a 5.1-channelaudio source reproduced by a 5.1-channel acoustic reproduction system atthe listening position by means of a microphone 140 and automaticallymeasures the transfer characteristics of each channel, while allowingnormal multi-channel reproduction to proceed.

Of the transfer characteristics measured by the transfer characteristicmeasuring device, the amplitude and the phase that relate to thetransfer function (frequency characteristics), the delay time and thepropagation time are displayed on the display section. Additionally, thetransfer characteristics measuring device can be used to update theparameters of each of the amplifiers of the amplifier section that areobjects of measurement and regulate each channel according to thetransfer characteristics.

In any transfer characteristics measuring devices according to theinvention as described above, all the object channels of measurement maybe selected for measurement or only the channels specified by the usermay be selected for measurement. For example, the front L channel, thefront C channel and the front R channel may be selected for measurement.

In other words, out of the objects of measurement of m=5 or 5.1, n=3 orthree object channels of measurement may be selected. m may be equal to2, 3, 4 or 6, 7, . . . n may also be equal to 2, 3, 4 or 6, 7, . . . solong as it is not greater than m.

A small value may be selected for the reference value of Z for thenumber of repetition that is used in the checking operation of Step S6shown in FIG. 7 when the transfer functions of the front L channel, thefront C channel and the front R channel are observed first out of thefive channels and those of the LS channel and the RS channel areobserved thereafter. For example, it may be reduced from 10 to 6 or 7.

It is possible to realize a transfer characteristics measuring deviceaccording to the invention by means of a personal computer by making theCPU of the personal computer execute a transfer characteristicsmeasuring computer program prepared on the basis of the sequence ofprocessing operation illustrated in FIGS. 7 through 9, 12 and 13.

Referring to FIG. 15, the CPU 210 of personal computer 200 is connectedto a ROM 230 storing such a transfer characteristics measuring computerprogram, a RAM 240 that provides a program work area, an amplifiersection and an I/F 250, which operates as interface between a microphoneand inputs IN₁, IN₂, by way of an internal bus 220.

The personal computer 200 reads out the transfer characteristicsmeasuring computer program from the ROM 230 and executes it, using theRAM 240 as work memory, to operate as transfer characteristics measuringdevice 1 or 100.

The personal computer 200 displays the characteristics including theamplitude and the phase obtained by means of the transfer function(frequency characteristics), the delay time, the propagation time andthe like on the display section thereof. The transfer function of eachamplifier of the amplifier section that is an object of measurement isused for updating the parameters of the amplifier.

The transfer function, the delay time and the propagation time arelisted as examples of the transfer characteristics to be observed by atransfer characteristics measuring device according to the invention.

The characteristics such as the amplitude and the phase obtained bymeans of the transfer function (frequency characteristics) of thetransfer characteristics that are measured by a transfer characteristicsmeasuring device according to the invention, the delay time, thepropagation time and the like can be displayed on the display sectionand used for updating the parameters of each amplifier of the amplifiersection that is an object of measurement m order to regulate eachchannel according to the transfer function.

Now, how the transfer characteristics are used in an actualmulti-channel acoustic reproduction environment will be described below.

The distance between each speaker and the listening position is definedfor an AV amplifier in many cases. Thus, propagation time is reduced todistance by using the speed of sound. The polarity of the speaker can bejudged to be positive or negative by the peak value of the impulseresponse of each channel. Thus, the level difference between twochannels can be determined by seeing the difference of the peak valuesof the time-energy curves of the channels. Then, it is possible todetermine the speaker size by seeing to the extent to which the lowfrequency band can be reproduced, referring to the amplitudecharacteristic of the transfer function. If there is no microphone inputsignal (or the level of the microphone input signal is lower than apredetermined value) while there is an original signal, it may be judgedthat the channel is not connected.

The present invention is by no means limited to the embodimentsdescribed above by referring to the accompanying drawings and it may beclear to those skilled in the art that the above described embodimentscan be modified and altered in many different ways without departingfrom the scope of the invention.

INDUSTRIAL APPLICABILITY

A transfer characteristics measuring device and a transfercharacteristics measuring method according to the invention canautomatically measure the transfer characteristics of each channel of amulti-channel acoustic reproduction system in a multi-channel acousticreproduction environment, while allowing normal multi-channelreproduction to proceed.

A transfer characteristics measuring computer program according to theinvention can make a computer to operate as a transfer characteristicsmeasuring device that can automatically measure the transfercharacteristics of each channel of a multi-channel acoustic reproductionsystem in a multi-channel acoustic reproduction environment, whileallowing the system to operate for normal multi-channel reproduction.

According to the invention, there is provided an amplifier in which thetransfer characteristics of each channel can be automatically measuredin a multi-channel acoustic reproduction environment.

Thus, according to the invention, it is possible to automaticallymeasure the transfer characteristics of each channel of a multi-channelacoustic reproduction system without the need of reproducing a test tonefor each channel on a channel by channel basis, while allowing normalmulti-channel reproduction to proceed.

Since surround signals are often used for sound effects, they mayfrequently be mute signals. Therefore, it may be necessary to detect andmeasure the surround signals contained in the source signal when theoriginal source signal is used. The present invention can accommodatesuch a situation.

1. A transfer characteristics measuring device for measuring transfercharacteristics of each of n objects of measurement out of m objects ofmeasurement, where n is less than or equal to m, using input signalsbeing input to the m objects of measurement and output signals from theobjects of measurement in an acoustic reproduction environment for mchannels having mutually differentiated respective spatial positions,the device comprising: object of measurement selecting means forselecting an object of measurement out of the n objects of measurementaccording to levels of the input signals of the m channels beingsupplied to the m objects of measurement; and transfer characteristicscomputing and determining means for: computing the transfercharacteristics of the object of measurement selected by the object ofmeasurement selecting means according to an input signal being suppliedto the object of measurement and an output signal of the object ofmeasurement corresponding to the input signal, and determining adoptionof the transfer characteristics of the object of measurement, excludingthe object of measurement from the m objects of measurement, wherein:the transfer characteristics computing and determining means includes:orthogonal transformation means for performing an orthogonaltransformation on the input signals supplied to the object ofmeasurement selected by the object of measurement selecting means and onthe output signals of the object of measurement corresponding to theinput signals; power spectrum computing means for computing powerspectrums of the input signals and power spectrums of the outputsignals, using spectrums of the input signals and spectrums of theoutput signals obtained by the orthogonal transformation means; crossspectrum computing means for multiplying a frequency component of thespectrum of each input signal by a frequency component of the spectrumof the corresponding output signal obtained by the orthogonaltransformation means to computationally determine cross spectrums;spectrum average computing means for computing an average value of thepower spectrums of the input signals, an average value of the powerspectrums of the output signals, and an average value of the crossspectrums; transfer characteristics computing means for computingtransfer characteristics of the object of measurement from the averagevalues of the power spectrums and the average value of the crossspectrums; coherence computing means for computing a value of thecoherence from the average value of the power spectrums of the inputsignals, the average value of the power spectrums of the output signalsand the average value of the cross spectrums; and transfercharacteristics determining means for determining adoption of thetransfer characteristics of the object of measurement according to thecoherence value and for excluding the object of measurement from theplurality of objects of measurement.
 2. The device according to claim 1,wherein the object of measurement selecting means includes: Intake meansfor taking in the input signals of the m channels being applied to the mobjects of measurement; Level detecting means for detecting the level ofeach of the input signals of the m channels taken in by the intakemeans; and Selecting means for selecting one of the objects ofmeasurement according to the levels detected by the level detectingmeans.
 3. The device according to claim 2, wherein the selecting meansof the object of measurement selecting means selects the object ofmeasurement that receives the input signal that shows the highest levelamong the input signals supplied to the m objects of measurement andtaken in during a predetermined time period by the intake means.
 4. Thedevice according to claim 2, wherein the selecting means of the objectof measurement selecting means selects the objects of measurement thatreceives the input signal that shows the highest level among the inputsignals supplied to the m objects of measurement and taken in during apredetermined time period by the intake means and, a level differencegreater than a predetermined value when compared with the other inputsignals.
 5. The device according to claim 2, wherein the selecting meansof the object of measurement selecting means selects the object ofmeasurement that is specified in the input signals supplied to the mobjects of measurement taken in during a predetermined time period bythe intake means and receives the input signal that shows the highestlevel.
 6. The device according to claim 1, wherein the transfercharacteristics determining means of the transfer characteristicscomputing and determining means determines transfer characteristics foreach measuring point on a frequency axis in the orthogonaltransformation when the coherence value is not smaller than a thresholdvalue showing that the object of measurement is not influenced by theother objects of measurement.
 7. The device according to claim 1,wherein the orthogonal transformation means of the transfercharacteristics computing and determining means repeats the orthogonaltransformation n times.
 8. The device according to claim 7, wherein thespectrum average computing means of the transfer characteristicscomputing and determining means computes the average values of the powerspectrums and the average value of the cross spectrums, using the numberof n times for which the orthogonal transformation means repeats theorthogonal transformation.
 9. The device according to claim 8, whereinthe transfer characteristics determining means of the transfercharacteristics computing and determining means determines the transfercharacteristics according to the average values of the power spectrumsand the average value of the cross spectrums according to the number ofn times for which the orthogonal transformation means repeats theorthogonal transformation similarly according to the coherence value.10. The device according to claim 6, wherein, when there is at least afrequency point where the coherence value is not greater than thethreshold value, the transfer characteristics determining means of thetransfer characteristics computing and determining means determinesadoption of the transfer characteristics, repeating a processingoperation of judging if the coherence value of the object of measurementis not smaller than the threshold value for a predetermined number oftimes Z.
 11. The device according to claim 10, wherein, when there is atleast a frequency point where the coherence value is not greater thanthe threshold value if the processing operation of judging is repeatedfor the predetermined number of times Z, the transfer characteristicsdetermining means of the transfer characteristics computing anddetermining means computes a transfer function of the frequency point,using already computed transfer functions of the other frequency points.12. The device according to claim 6, wherein, when there is at least afrequency point where the coherence value is not greater than thethreshold value, the transfer characteristics determining means of thetransfer characteristics computing and determining means determinesadoption of the transfer characteristics by judging if a coherence valueof a new object of measurement selected by the object of measurementselecting means is not smaller than the threshold value and repeating aprocessing operation of judging if the coherence value of each of theselected objects of measurement is not smaller than the threshold valuefor a predetermined number of times Z.
 13. The device according to claim12, wherein, when there is at least a frequency point where thecoherence value is not greater than the threshold value if theprocessing operation of judging is repeated for the predetermined numberof times Z, the transfer characteristics determining means of thetransfer characteristics computing and determining means computes atransfer function of the frequency point, using already computedtransfer functions of the other frequency points.
 14. The deviceaccording to claim 1, wherein, when there is at least an object ofmeasurement adapted to be in charge of a frequency band not higher than120 Hz out of the m objects of measurement, the transfer characteristicsdetermining means of the transfer characteristics computing anddetermining means makes transfer functions of the remaining objects ofmeasurement for the same frequency band unrelated to the coherencevalue.
 15. The device according to claim 1, further comprising:parameter output means for outputting parameters relating to thetransfer characteristics of the n objects of measurement according to atransfer function, adoption of which is determined by the transfercharacteristics computing and determining means.
 16. A transfercharacteristics measuring method for measuring the transfercharacteristics of each of n objects of measurement out of m objects ofmeasurement, wherein n is less than or equal to m, using input signalsbeing input to the m objects of measurement and output signals from theobjects of measurement in an acoustic reproduction environment for mchannels having mutually differentiated respective spatial positions,the method comprising: an object of measurement selecting step forselecting an object of measurement out of the n objects of measurementaccording to levels of the input signals of the m channels beingsupplied to the m objects of measurement; and a transfer characteristicscomputing and determining step of: computing the transfercharacteristics of the object of measurement selected in the object ofmeasurement selecting step according to an input signal being suppliedto the object of measurement and an output signal of the object ofmeasurement corresponding to the input signal, and determining adoptionof the transfer characteristics of the object of measurement, excludingthe object of measurement from the m objects of measurement, wherein:the transfer characteristics computing and determining step includes: anorthogonal transformation step of performing an orthogonaltransformation on the input signals supplied to the object ofmeasurement selected in the object of measurement selecting step and onthe output signals of the object of measurement corresponding to theinput signals; a power spectrum computing step of computing powerspectrums of the input signals and power spectrums of the outputsignals, using spectrums of the input signals and spectrums of theoutput signals obtained by the orthogonal transformation step; a crossspectrum computing step of multiplying a frequency component of thespectrum of each input signal by a frequency component of the spectrumof the corresponding output signal obtained by the orthogonaltransformation step to computationally determine cross spectrums; aspectrum average computing step of computing an average value of thepower spectrums of the input signals, an average value of the powerspectrums of the output signals, and an average value of the crossspectrums; a transfer characteristics computing step of computingtransfer characteristics of the object of measurement from the averagevalues of the power spectrums and the average value of the crossspectrums; a coherence computing step of computing a value of thecoherence from the average value of the power spectrums of the inputsignals, the average value of the power spectrums of the output signalsand the average value of the cross spectrums; and a transfercharacteristics determining step of determining adoption of the transfercharacteristics of the object of measurement according to the coherencevalue and of excluding the object of measurement from the plurality ofobjects of measurement.
 17. A transfer characteristics measuring devicefor measuring the transfer characteristics of each of n objects ofmeasurement out of m objects of measurement where n is less than orequal to m, using input signals being input to the m objects ofmeasurement and output signals from the objects of measurement in anacoustic reproduction environment for m channels having mutuallydifferentiated respective spatial positions, the device comprising:object of measurement selecting means for selecting an object ofmeasurement according to levels of the input signals of the m channelsbeing supplied to the m objects of measurement; and transfercharacteristics computing and determining means for computing thetransfer characteristics of the object of measurement selected by theobject of measurement selecting means according to an input signal beingsupplied to the object of measurement and an output signal of the objectof measurement corresponding to the input signal for each frequencypoint and adopting the transfer characteristics of the object ofmeasurement in concurrence with computing and adopting of the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting means from the n objects of measurementfor each frequency point, wherein: the transfer characteristicscomputing and determining means includes: orthogonal transformationmeans for performing an orthogonal transformation on the input signalssupplied to the object of measurement selected by the object ofmeasurement selecting means and on the output signals of the object ofmeasurement corresponding to the input signals; power spectrum computingmeans for computing power spectrums of the input signals and powerspectrums of the output signals, using spectrums of the input signalsand spectrums of the output signals obtained by the orthogonaltransformation means; cross spectrum computing means for multiplying afrequency component of the spectrum of each input signal by a frequencycomponent of the spectrum of the corresponding output signal obtained bythe orthogonal transformation means to computationally determine crossspectrums; spectrum average computing means for computing an averagevalue of the power spectrums of the input signals, an average value ofthe power spectrums of the output signals, and an average value of thecross spectrums; transfer characteristics computing means for computingtransfer characteristics of the object of measurement from the averagevalues of the power spectrums and the average value of the crossspectrums; coherence computing means for computing a value of thecoherence from the average value of the power spectrums of the inputsignals, the average value of the power spectrums of the output signalsand the average value of the cross spectrums; and transfercharacteristics determining means for determining adoption of, for eachfrequency point, the transfer characteristics of the object ofmeasurement according to the coherence value in concurrence withcomputation and adoption for each frequency point of the transfercharacteristics of each of the objects of measurement selected out ofthe n objects of measurement by the object of measurement selectingmeans.
 18. A transfer characteristics measuring device for measuring thetransfer characteristics of each of n objects of measurement out of mobjects of measurement where n is less than or equal to m, using inputsignals being input to the m objects of measurement and output signalsfrom the objects of measurement in an acoustic reproduction environmentfor m channels having mutually differentiated respective spatialpositions, the device comprising: object of measurement selecting meansfor selecting an object of measurement according to levels of the inputsignals of the m channels being supplied to the m objects ofmeasurement; and transfer characteristics computing and determiningmeans for computing the transfer characteristics of the object ofmeasurement selected by the object of measurement selecting meansaccording to an input signal being supplied to the object of measurementand an output signal of the object of measurement corresponding to theinput signal for each frequency point and adopting the transfercharacteristics of the object of measurement in concurrence withcomputing and adopting of the transfer characteristics of each of theobjects of measurement selected by the object of measurement selectingmeans from the n objects of measurement for each frequency point,wherein: the object of measurement selecting means includes: intakemeans for taking in the input signals of the m channels being suppliedto the m objects of measurement; level detecting means for detecting thelevel of each of the input signals of the m channels taken in by theintake means; and selecting means for selecting one of the objects ofmeasurement according to the levels detected by the level detectingmeans, wherein the object of measurement selecting means selects anobject of measurement that is specified in the input signals supplied tothe m objects of measurement and taken in during a predetermined timeperiod by the intake means and receives the input signal that shows ahighest level.
 19. The device according to claim 17, wherein thetransfer characteristics determining means of the transfercharacteristics computing and determining means determines transfercharacteristics for each measuring point on a frequency axis in theorthogonal transformation when the coherence value is not smaller than athreshold value showing that the object of measurement is not influencedby the other objects of measurement.
 20. The device according to claim17, wherein the orthogonal transformation means of the transfercharacteristics computing and determining means repeats the orthogonaltransformation n times.
 21. The device according to claim 20, whereinthe spectrum average computing means of the transfer characteristicscomputing and determining means computes the average values of the powerspectrums and the average value of the cross spectrums, using the numberof n times for which the orthogonal transformation means repeats theorthogonal transformation.
 22. The device according to claim 21, whereinthe transfer characteristics determining means of the transfercharacteristics computing and determining means determines the transfercharacteristics according to the average values of the power spectrumsand the average value of the cross spectrums according to the number ofn times for which the orthogonal transformation means repeats theorthogonal transformation similarly according to the coherence value.23. The device according to claim 20, wherein, when there is at least afrequency point where the coherence value is not greater than thethreshold value, the transfer characteristics determining means of thetransfer characteristics computing and determining means determinesadoption of the transfer characteristics by judging if the coherencevalue of a new object of measurement selected by the object ofmeasurement selecting means out of the n objects of measurementincluding the object of measurement is not smaller than the thresholdvalue and repeating a processing operation of judging if the coherencevalue of each of the selected objects of measurement is not smaller thanthe threshold value for a predetermined number of times Z.
 24. Thedevice according to claim 23, wherein, when there is at least afrequency point where the coherence value is not greater than thethreshold value if the processing operation of judging is repeated forthe predetermined number of times Z, the transfer characteristicsdetermining means of the transfer characteristics computing anddetermining means computes a transfer function of the frequency point,using already computed transfer functions of the other frequency points.25. The device according to claim 17, wherein, when there is at least anobject of measurement adapted to be in charge of a frequency band nothigher than 120 Hz out of the m objects of measurement, the transfercharacteristics determining means of the transfer characteristicscomputing and determining means makes transfer functions of theremaining objects of measurement for the same frequency band unrelatedto the coherence value.
 26. A transfer characteristics measuring methodfor measuring the transfer characteristics of each of n objects ofmeasurement out of m objects of measurement, where n is less than orequal to m, using input signals being input to the m objects ofmeasurement and output signals from the objects of measurement in anacoustic reproduction environment for m channels having mutuallydifferentiated respective spatial positions, the method comprising: anobject of measurement selecting step of selecting an object ofmeasurement according to levels of the input signals of the m channelsbeing supplied to the m objects of measurement; and a transfercharacteristics computing and determining step of: computing thetransfer characteristics of the object of measurement selected in theobject of measurement selecting step according to an input signal beingsupplied to the object of measurement and an output signal of the objectof measurement corresponding to the input signal for each frequencypoint and adopting the transfer characteristics of the object ofmeasurement in concurrence with computing and adopting of the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting step from the n objects of measurementfor each frequency point, wherein: the transfer characteristicscomputing and determining step includes: an orthogonal transformationstep of performing an orthogonal transformation on the input signalssupplied to the object of measurement selected in the object ofmeasurement selecting step on and the output signals of the object ofmeasurement corresponding to the input signals; a power spectrumcomputing step of computing power spectrums of the input signals andpower spectrums of the output signals, using spectrums of the inputsignals and spectrums of the output signals obtained by the orthogonaltransformation step; a cross spectrum computing step of multiplying afrequency component of the spectrum of each input signal by a frequencycomponent of the spectrum of the corresponding output signal obtained bythe orthogonal transformation step to computationally determine crossspectrums; a spectrum average computing step of computing an averagevalue of the power spectrums of the input signals, and an average valueof the power spectrums of the output signals, and an average value ofthe cross spectrums; a transfer characteristics computing step ofcomputing transfer characteristics of the object of measurement from theaverage values of the power spectrums and the average of the crossspectrums; a coherence computing step of computing a value of thecoherence from the average value of the power spectrums of the inputsignals, the average value of the power spectrums of the output signalsand the average value of the cross spectrums; and a transfercharacteristics determining step of determining adoption of, for eachfrequency point, the transfer characteristics of the object ofmeasurement according to the coherence value in concurrence withcomputation and adoption for each frequency point of the transfercharacteristics of each of the objects of measurement selected out ofthe n objects of measurement in the object of measurement selectingstep.
 27. A transfer characteristics measuring computer program recordedon a computer readable medium to be executed by a transfercharacteristics measuring device for measuring the transfercharacteristics of each of n objects of measurement out of m objects ofmeasurement, where n is less than or equal to m, using input signalsbeing input to the m objects of measurement and output signals from theobjects of measurement in an acoustic reproduction environment for mchannels having mutually differentiated respective spatial positions,the computer program comprising instructions for executing: an object ofmeasurement selecting step of selecting an object of measurementaccording to levels of the input signals of the m channels beingsupplied to the m objects of measurement; and a transfer characteristicscomputing and determining step of: computing the transfercharacteristics of the object of measurement selected in the object ofmeasurement selecting step according to an input signal being suppliedto the object of measurement and an output signal of the object ofmeasurement corresponding to the input signal for each frequency pointand adopting of the transfer characteristics of the object ofmeasurement in concurrence with computing and adopting the transfercharacteristics of each of the objects of measurement selected by theobject of measurement selecting step from the n objects of measurementfor each frequency point, wherein: the transfer characteristicscomputing and determining step, includes: an orthogonal transformationstep of performing an orthogonal transformation on the input signalssupplied to the object of measurement selected in the object ofmeasurement selecting step and on the output signals of the object ofmeasurement corresponding to the input signals; a power spectrumcomputing step of computing power spectrums of the input signals andpower spectrums of the output signals, using spectrums of the inputsignals and spectrums of the output signals obtained by the orthogonaltransformation step; a cross spectrum computing step of for multiplyinga frequency component of the spectrum of each input signal by afrequency component of the spectrum of the corresponding output signalobtained by the orthogonal transformation step to computationallydetermine cross spectrums; a spectrum average computing step ofcomputing an average value of the power spectrums of the input signals,and an average value of the power spectrums of the output signals, andan average value of the cross spectrums; a transfer characteristicscomputing step of computing transfer characteristics of the object ofmeasurement from the average values of the power spectrums and theaverage of the cross spectrums; a coherence computing step of computinga value of the coherence from the average value of the power spectrumsof the input signals, the average value of the power spectrums of theoutput signals and the average value of the cross spectrums; and atransfer characteristics determining step of determining adoption of,for each frequency point, the transfer characteristics of the object ofmeasurement according to the coherence value in concurrence withcomputation and adoption for each frequency point of the transfercharacteristics of each of the objects of measurement selected out ofthe n objects of measurement in the object of measurement selectingstep.